The 'E' Type Forum

Hi

I have sorted out my mixture problems but another problem has reared its ugly head.
After about 10 miles or so the car starts to misfire under load (acceleration). The tacho starts to bounce (electric) if thats a clue. I have fitted a new coil (correct one) and plugs but no difference. Before I replace all the electrics in one go can anyone make a suggestion. Could it be the condenser. I would like to pinpoint the faulty part if possible.

Many thanks
Keith
1970 2+2

Check that none of the carb pistons are sticking.

If the electronic tacho on an S2 is bouncing in association with the misfire it points unquestionably to ignition problems . I doubt that it would be condenser : this usually shows itself by a refusal to start from cold , although I suppose it could be breaking down internally whilst hot - and I don't think it would show up on the tacho as that counts the impulses rather than the level of the LT voltage. Also, with a failed condenser you would quickly burn the points radically because of arcing . A more likely source would be sticking points or a setting which altered for some reason when hot. It might also be worth checking the integrity of the white wire ( and its connectors ) which goes through the inductive coil on the back of the tacho, since if this is fatigued or has broken strands, it could well cause an intermittent ignition failure

Points and condenser are both cheap enough on this setup and I would start by changing those - if the problem persists I would suspect a wiring problem

Have you changed the plug caps? The integrated suppression resistors can fail so worth buying a complete new set with the pretty bow tie on.

Try a new rotor arm, I had a similar issue after approximately 5miles and found faulty rotor arm was arcing to earth.

Both the plug caps and the rotor arm can cause hot misfiring as suggested, although rotor arm conductivity usually results in a total stoppage rather than a miss . However, neither of these would have any effect on the tacho. That, to me, points definitely to a low tension circuit problem , and it is there I would be looking first

Agreed, however, my rotor arm fault manifested as a miss at approx 3000rpm when accelerating. Eventually cutting the engine dead but always allowing me to restart after a cool down period. The tachometer was affected but purely thru rpm glitches as the engine power cut and then increased as the rotor arm began to break down.

I had a problem with my Elan which I traced to a faulty rotor arm. As revs increased it seems a microscopic crack widened causing the misfire. Not a problem at low revs so was a real bugger to diagnose!

My experiences with rotor-arm tracking echos Christopher's. Once tracked, everything stopped. It was never an intermittent problem. It happened with alarming regularity on an MGA I owned in the early 1980s, and always with aftermarket rotors. I never had a problem with Lucas rotors.

Hi again.
Thanks to all the suggestions I finally found the culprit. It was the condenser.
Thanks again for everyones help.
Keith